Etch-resistant inkjet inks for manufacturing conductive patterns

ABSTRACT

A UV curable inkjet ink includes a polymerizable composition, wherein at least 80 wt % of the polymerizable composition consists of: a) 15.0 to 70.0 wt % of an acryl amide; b) 20.0 to 75.0 wt % of a polyfunctional acrylate; and c) 1.0 to 15.0 wt % of a monofunctional (meth)acrylate containing a carboxylic acid group, a phosphoric acid group, or a phosphonic acid group; with all weight percentages (wt %) based on the total weight of the polymerizable composition.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a 371 National Stage Application ofPCT/EP2015/071147, filed Sep. 16, 2015. This application claims thebenefit of European Application No. 14186726.7, filed Sep. 29, 2014,which is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an etch-resistant inkjet ink and amethod of manufacturing conductive patterns.

2. Description of the Related Art

Printed circuit boards are usually made by coating a photo resist layeron a copper sheet bonded to a non-conductive substrate, applying atemporary UV mask of a negative image of a desired conductive pattern,UV exposing the photo resist layer, removing the non-exposed photoresist layer by a developer, removing unwanted copper by etching,removing the exposed photo resist layer by an alkaline stripping bath,thereby leaving only the desired conductive copper pattern present onthe non-conductive substrate.

Etching is the process of using a chemical, usually a strong acid ormordant, to cut into the unprotected parts of a metal surface. The useof developer to remove the photo resist layer, often 50 μm thick ormore, results in extra cost and chemical waste. Therefore, it has beeninvestigated if the developing step could be eliminated by UV curableinkjet printing an etch-resistant inkjet ink layer on the copper sheet,which after etching is removed in flakes by an alkaline stripping bathto expose the conductive copper pattern.

U.S. Pat. No. 5,270,368 (VIDEOJET) discloses a UV curable,etch-resistant ink for inkjet printing circuit boards comprising a resinformulation having at least two acrylate components, one of which is anaromatic acrylate having a pendant carboxyl group and one of which is anacrylated epoxy monomer or dimer, a photoinitiator and an organiccarrier. The preferred organic carrier of methanol and methyl ethylketone is employed in a range of 40% to 90% by weight of the inkcomposition. These volatile organic solvents lead to latency problems ofinkjet print heads making reliable inkjet printing in an industrialenvironment process problematic. Reducing the amount of organic solventleads to a too high ink viscosity, because some aromatic acrylatecompounds traditionally used for preparing photo resist coatings havevery high viscosity. For example, the bisphenol A ethoxylated diacrylate(Photomer™ 4028) used in all the examples of U.S. Pat. No. 5,270,368(VIDEOJET) has a viscosity of 800 to 1200 mPa·s at 25° C. These aromaticacrylate compounds are essential for having a good balance in adhesionso that the printed ink layer is etch resistant yet easily removableafter etching, especially since many different etching conditions andetchants are used in industry.

WO 2004/106437 A (AVECIA) discloses a process for etching a metal oralloy surface which comprises applying an etch-resistant ink by inkjetprinting to selected areas of the metal or alloy, exposing theetch-resistant ink to actinic radiation and/or particle beam radiationto effect polymerisation, optionally thermally treating theetch-resistant ink and then removing the exposed metal or alloy by achemical etching process wherein the etch-resistant ink is substantiallysolvent-free.

Another problem is the flake formation in the alkaline stripping bath.Stripping solutions are normally alkaline metal hydroxides, such assodium or potassium hydroxide, or based on amines such as mono or triethanolamine and tetra methyl ammonium hydroxide. The stripping solutionbreaks the polymer chain at the cross-linking point of the threedimensional structure, which is formed during the polymerization of theresist and before the bond between the resist and the copper surface isbroken. In order to extend the working lifetime of the strippingsolution, it is necessary to filter the solution to remove the strippedflakes of resist. If the flake size is too large it tends to adhere tostripping equipment disturbing the smooth running of the manufacturingprocess. If the flakes are too small they pass through the filter andreturn in the stripping bath. After a while these small flakesaccumulate and also start to disturb the smooth running of themanufacturing process. These very small flakes tend to block the nozzlesof the sprays of the stripping line. The stripped flake size depends onthe type of stripping solution, the concentration of the strippingsolution, the temperature of the stripping solution and the design ofthe stripping equipment, etc. This multitude of influencing factorsmakes it very difficult to control the flake size to a desired size.

Hence, there remains a need for improved low viscous radiation curableinkjet inks suitable for reliable inkjet printing in an industrialetching process applicable to a wide range of etchants and etchingconditions and exhibiting no problems with stripping and flakeformation.

SUMMARY OF THE INVENTION

In order to overcome the problems described above, preferred embodimentsof the present invention provide a UV curable inkjet ink as definedbelow.

It was found that a very specific composition of UV curable inkjet inkwas capable of combining all the requirements of cure speed, etchresistance, strippability and flake formation.

Further objects of the invention will become apparent from thedescription hereinafter

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Definitions

The term “monofunctional” means that the monomer or oligomer includesone free radical polymerizable group.

The term “polyfunctional” means that the monomer or oligomer includestwo or more free radical polymerizable groups. For example, apolyfunctional acrylate contains two, three or more acrylate groups asfree radical polymerizable groups.

The term “alkyl” means all variants possible for each number of carbonatoms in the alkyl group i.e. methyl, ethyl, for three carbon atoms:n-propyl and isopropyl; for four carbon atoms: n-butyl, isobutyl andtertiary-butyl; for five carbon atoms: n-pentyl, 1,1-dimethyl-propyl,2,2-dimethylpropyl and 2-methyl-butyl, etc.

Unless otherwise specified a substituted or unsubstituted alkyl group ispreferably a C₁ to C₆-alkyl group.

Unless otherwise specified a substituted or unsubstituted alkenyl groupis preferably a C₁ to C₆-alkenyl group.

Unless otherwise specified a substituted or unsubstituted alkynyl groupis preferably a C₁ to C₆-alkynyl group.

Unless otherwise specified a substituted or unsubstituted aralkyl groupis preferably a phenyl or naphthyl group including one, two, three ormore C₁ to C₆-alkyl groups.

Unless otherwise specified a substituted or unsubstituted alkaryl groupis preferably a C₇ to C₂₀-alkyl group including a phenyl group ornaphthyl group.

Unless otherwise specified a substituted or unsubstituted aryl group ispreferably a phenyl group or naphthyl group.

Unless otherwise specified a substituted or unsubstituted heteroarylgroup is preferably a five- or six-membered ring substituted by one, twoor three oxygen atoms, nitrogen atoms, sulphur atoms, selenium atoms orcombinations thereof.

The term “substituted”, in e.g. substituted alkyl group means that thealkyl group may be substituted by other atoms than the atoms normallypresent in such a group, i.e. carbon and hydrogen. For example, asubstituted alkyl group may include a halogen atom or a thiol group. Anunsubstituted alkyl group contains only carbon and hydrogen atoms

Unless otherwise specified a substituted alkyl group, a substitutedalkenyl group, a substituted alkynyl group, a substituted aralkyl group,a substituted alkaryl group, a substituted aryl and a substitutedheteroaryl group are preferably substituted by one or more constituentsselected from the group consisting of methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl and tertiary-butyl, ester, amide, ether,thioether, ketone, aldehyde, sulfoxide, sulfone, sulfonate ester,sulphonamide, —Cl, —Br, —I, —OH, —SH, —CN and —NO₂.

UV Curable Inkjet Inks

A UV curable inkjet ink according to a preferred embodiment of theinvention comprises a polymerizable composition, wherein at least 80 wt%, preferably at least 90 wt % and most preferably 100 wt % of thepolymerizable composition consists of:

a) 15.0 to 70.0 wt % of an acryl amide;

b) 20.0 to 75.0 wt % of a polyfunctional acrylate; and

c) 1.0 to 15.0 wt % of a monofunctional (meth)acrylate containing acarboxylic acid group, a phosphoric acid group or a phosphonic acidgroup; with all weight percentages (wt %) based on the total weight ofthe polymerizable composition.

The UV curable inkjet inks may also be cationically curable, but arepreferably free radical UV curable inkjet inks. The UV curable inkjetinks can be cured by e-beam, but are preferably cured by UV light.

The UV curable ink may be a colourless inkjet ink, but preferably itcontains at least one colorant. The advantage is that the printed inkpattern is clearly visible which allows orienting the metal surfaceduring handling and to visually inspect the quality of a PCBmanufacturing process by the naked eye. The colorant may be a dye or apigment. If the colorant is a pigment preferably a dispersant ispresent, more preferably a polymeric dispersant. The pigmented curableink may contain a dispersion synergist to improve the dispersion qualityand stability of the ink. However, most preferably the colorant is a dyethat survives the UV curing step in the inkjet printing process. A dyecauses unlike pigments and dispersants usually no sludge in the etchingand stripping solutions.

For reliable industrial inkjet printing, the viscosity of the UV curableinkjet inks is preferably no more than 20 mPa·s at 45° C., morepreferably between 1 and 18 mPa·s at 45° C., and most preferably between4 and 14 mPa·s at 45° C.

For good image quality and adhesion, the surface tension of the UVcurable inkjet inks is preferably in the range of 18 mN/m to 70 mN/m at25° C., more preferably in the range of about 20 mN/m to about 40 mN/mat 25° C.

Methods of Inkjet Printing and Manufacturing Conductive Patterns

A method of inkjet printing according to a preferred embodiment of theinvention includes the steps of a) forming a protected area on a metalsurface by printing and curing a UV curable inkjet ink on the metalsurface;

b) removing metal from the unprotected area of the metal surface byetching; and c) removing at least partially the cured UV curable inkjetink from the protected area of the metal surface; wherein the UV curableinkjet ink comprises a polymerizable composition, wherein at least 80 wt% of the polymerizable composition consists of:

a) 15.0 to 70.0 wt % of an acryl amide;

b) 20.0 to 75.0 wt % of a polyfunctional acrylate; and

c) 1.0 to 15.0 wt % of a monofunctional (meth)acrylate containing acarboxylic acid group, a phosphoric acid group or a phosphonic acidgroup; with all weight percentages (wt %) based on the total weight ofthe polymerizable composition.

In one preferred embodiment, the inkjet printing method is used formanufacturing a conductive pattern. In this case, the metal surface ispreferably a metal foil, most preferably a copper foil, attached to asubstrate. There is no real limitation on the type of substrate bondedto the metal sheet as long as it is non-conductive. The substrates maybe made of a ceramic, glass or plastics, such as polyimides. The metalsheet, usually having a thickness between 9 and 105 μm, bonded to thesubstrate is preferably a copper sheet, because copper has a highconductivity and is relatively cheap.

In another preferred embodiment, the inkjet printing method is used formanufacturing a decorative etched metal panel. In this case, preferablya solid metal panel is used. However, also a metal foil attached to asubstrate may be used. There is no real limitation on the type ofsubstrate bonded to the metal foil. The substrates may be made of aceramic, glass or plastics, or even a second (cheaper) metal plate. Themetal may also be an alloy.

In both cases of conductive and decorative patterns, the etched metal oralloy substrate printed with a UV curable inkjet ink preferably containscopper.

There is no limitation on the nature of the metal surface. The metalsurfaces preferably consist of copper, aluminium, nickel, iron, tin,titanium or zinc, but may be also alloys including these metals. In avery preferred embodiment, the metal surface is made of copper. Copperhas a high electrical conductivity and is a relatively cheap metal,making it very suitable for making printed circuit boards.

The metal surface may be self-supporting or may be present on a support.The support can be a non-flexible support as conventionally used in theproduction of PCBs, but may be also a flexible substrate made of e.g.polyethylene terephthalate or polyimide.

Self supporting metal surfaces are generally used when a decorativemetal panel is made. Such a decorative metal panel may serve a purposeother than being purely decorative, such as providing information. Forexample, an aluminium name plate wherein the etch resistant UV curableinkjet ink was printed as information, such as a name of a person or acompany, and then removed to result in a glossy shiny name on a matetched background, is also considered a decorative metal panel includinga decorative element. Etching causes a change in optical properties of ametal surface, such as a change of gloss. After removal of the cured UVcurable inkjet ink from the metal surface an aesthetic effect is createdbetween the etched and the non-etched metal surface.

In another preferred embodiment of a decorative metal panel, the metalsurface is not self-supporting and when removed by etching exposes thecolour of or the information on the support.

In a preferred embodiment of the inkjet printing method, the metalsurface is cleaned before printing the UV curable inkjet ink. This isespecially desirable when the metal surface is handled by hand and nogloves are worn. The cleaning removes dust particles and grease whichcan interfere in the adhesion of the UV curable inkjet ink to the metalsurface.

Etching of a metal surface, as in step b) of the inkjet printing method,is performed by using an etchant. The etchant is preferably an aqueoussolution having a pH<3 or wherein 8<pH<10.

In a preferred embodiment, the etchant is an acid aqueous solutionhaving a pH of less than 2. The acid etchant preferably includes atleast one acid selected from the group consisting of nitric acid, picricacid, hydrochloric acid, hydrofluoric acid and sulphuric acid.

Preferred etchants known in the art include Kalling's No 2, ASTM No 30,Kellers Etch, Klemm's Reagent, Kroll's Reagent, Marble's Reagent,Murakami's Reagent, Picral and Vilella's Reagent.

In another preferred embodiment, the etchant is an alkaline aqueoussolution having a pH of no more than 9. The alkaline etchant preferablyincludes at least one base selected from the group consisting of ammoniaor ammonium hydroxide, potassium hydroxide and sodium hydroxide.

The etchant may also contain a metal salt such as copper dichloride,copper sulphate, potassium ferricyanide and iron trichloride.

Etching is preferably performed in a time frame of seconds to a fewminutes, more preferably 5 to 150 seconds. Etching is preferablyperformed at a temperature between 35 and 50° C.

Etching is preferably followed by rinsing with water to remove anyresidual etchant.

After etching, the cured UV curable inkjet ink must at least partiallybe removed from the metal surface, so that e.g. electric or electronicdevices can make contact with the remaining metal surface (conductivepattern) or that the decorative feature of an etched metal panel becomesfully visible. For example, an electronic component such as a transistormust be able to make electrical contacts with the conductive (copper)pattern on the printed circuit board. In a preferred embodiment, thecured UV curable inkjet ink is completely removed from the metalsurface.

In a preferred embodiment, the cured UV curable inkjet ink is removedfrom the protected area in step c) by an alkaline stripping bath. Suchan alkaline stripping bath is usually an aqueous solution with a pH>10.

In another preferred embodiment, the cured UV curable inkjet ink isremoved from the protected area in step c) by dry delamination. Thistechnique of “dry stripping” is currently unknown in the art ofmanufacturing printed circuit boards and introduces several ecologicaland economical advantages in the manufacturing process. Dry strippingnot only eliminates the need of a corrosive alkaline stripping bath andits inherent liquid waste, but also allows for a higher throughput. Drystripping can be implemented, for example, by using an adhesive foil anda roll-to-roll laminator-delaminator. The adhesive foil is firstlaminated with its adhesive side onto the cured UV curable inkjet inkpresent on the metal surface and subsequently delaminated therebyremoving the cured UV curable inkjet ink from the metal surface.Delamination by a roll-to-roll laminator-delaminator can be performed inseconds, while alkaline stripping can take minutes.

Acryl Amides

The UV curable inkjet ink according to a preferred embodiment includesat least 15.0 to 70.0 wt %, preferably at least 20.0 to 65.0 wt % andmost preferably at least 30.0 to 60.0 wt % of an acryl amide in thepolymerizable composition, with all weight percentages (wt %) based onthe total weight of the polymerizable composition.

A single acryl amide or a mixture of acryl amides may be used.

Preferred acryl amides are disclosed in Table 1.

TABLE 1 AA-1

AA-2

AA-3

AA-4

AA-5

AA-6

AA-7

AA-8

AA-9

AA-10

In a preferred embodiment of the UV curable inkjet ink, the acryl amideis a cyclic acryl amide.

In the most preferred embodiment of the UV curable inkjet ink, the acrylamide is acryloyl morpholine.

Polyfunctional Acrylates

The UV curable inkjet ink according to a preferred embodiment includesat least 20.0 to 75.0 wt %, preferably at least 30.0 to 65.0 wt % andmost preferably at least 40.0 to 55.0 wt % of a polyfunctional acrylatein the polymerizable composition, with all weight percentages (wt %)based on the total weight of the polymerizable composition.

A single polyfunctional acrylate or a mixture of polyfunctionalacrylates may be used.

In a preferred embodiment, the polyfunctional acrylate is selected fromthe group consisting of dipropylene glycol diacrylate, neopentylglycoldiacrylate, neopentylglycol (2× propoxylated) diacrylate, pentaerythritol tetraacrylate, 1,6-hexanediol diacrylate, trimethylolpropanetriacrylate, ethoxylated trimethylolpropane triacrylate, tripropyleneglycol diacrylate, ditrimethyloylpropane tetraacrylate, ethoxylatedpentaerythritol tetraacrylate, and polyethyleneglycol diacrylate.

In the most preferred embodiment of the UV curable inkjet ink, thepolyfunctional acrylate includes a neopentylglycol hydroxy pivalatediacrylate.

Acid Group Containing (Meth)Acrylates

The UV curable inkjet ink according to a preferred embodiment includesat least 1 to 15 wt %, preferably at least 2 to 12 wt % and mostpreferably at least 4 to 8 wt % of a (meth)acrylate containing acarboxylic acid group, a phosphoric acid group or a phosphonic acidgroup in the polymerizable composition, with all weight percentages (wt%) based on the total weight of the polymerizable composition.

Suitable examples of the carboxylic acid group-containing monofunctional(meth)acrylate include a compound represented by the Formula (I):

wherein, R represents a hydrogen atom or a methyl group, preferably ahydrogen atom; and Z represents a divalent organic group.

Preferred examples of Z are —(CH2)n-* [wherein n represents an integerof 2 to 12]; *—CH2-CH2-O—CO—Z′-* [wherein Z′ represents a divalentorganic group selected from the following]; *—C6H4-*; *—C6H4-(CH2)n-*[wherein n represents an integer of 1 to 12]; *—(CH2)n-C6H4-* [wherein nrepresents an integer of 1 to 12]; and —(CH2)n-O—C6H4-* [wherein nrepresents an integer of 1 to 12]; and wherein * represents a linkingsite.

Preferred examples of the (meth)acrylate containing a carboxylic acidgroup are discloses in Table 2.

TABLE 2 MC-1

MC-2

MC-3

MC-4

Preferred examples of the (meth)acrylate containing a phosphoric acidgroup or a phosphonic acid group include 2-(methacryloyloxy) ethylphosphate, hydroxyethyl methacrylate phosphate, bis-(2-methacryloyloxyethyl) phosphate.

Preferred examples of the (meth)acrylate containing a phosphoric acidgroup are compounds according to Formula P-1 or P-2:

wherein R represents C_(n)H_(2n+1) with n representing an integerbetween 6 and 18.

Preferred examples of the (meth)acrylate containing a phosphoric acidgroup are disclosed in Table 3.

TABLE 3 MP-1

with n = 2 to 8 MP-2

with n = 2 to 8 MP-3

In a particularly preferred embodiment of the UV curable inkjet ink, the(meth)acrylate containing a carboxylic acid group, a phosphoric acidgroup, or a phosphonic acid group is selected from the group consistingof: 2-carboxyethyl acrylate, 2-acryloyl ethyl succinate, and2-hydroxyethyl methacrylate phosphate.

Other Polymerizable Compounds

Other polymerizable compounds than the ones above may be present in theUV curable inkjet ink in an amount of 0 to 20 wt %, more preferably upto 15 wt % and most preferably in an amount of up to 10 wt % with allweight percentages (wt %) based on the total weight of the polymerizablecomposition.

The other polymerizable compounds preferably consist of one or moremonomers, oligomers and/or prepolymers. These monomers, oligomers and/orprepolymers may possess different degrees of functionality, A mixtureincluding combinations of mono-, di-, tri- and higher functionalitymonomers, oligomers and/or prepolymers may be used.

Particularly preferred other monomers and oligomers are those listed in[0106] to [0115] in EP 1911814 A (AGFA).

Colorants

The UV curable inkjet may be a substantially colourless inkjet ink, butpreferably the UV curable inkjet ink includes at least one colorant. Thecolorant makes the temporary mask clearly visible to the manufacturer ofconductive patters, allowing a visual inspection of quality.

The colorant in the cured inkjet ink pattern on the metal sheet and theUV curable inkjet ink may be a pigment or a dye, but is preferably a dyethat is not bleached by the UV curing step during the inkjet printingprocess of the UV curable inkjet ink.

The pigments may be black, white, cyan, magenta, yellow, red, orange,violet, blue, green, brown, mixtures thereof, and the like. A colourpigment may be chosen from those disclosed by HERBST, Willy, et al.Industrial Organic Pigments, Production, Properties, Applications. 3rdedition. Wiley—VCH, 2004. ISBN 3527305769.

Suitable pigments are disclosed in paragraphs [0128] to [0138] of WO2008/074548 (AGFA GRAPHICS).

Pigment particles in inkjet inks should be sufficiently small to permitfree flow of the ink through the inkjet-printing device, especially atthe ejecting nozzles. It is also desirable to use small particles formaximum colour strength and to slow down sedimentation. Most preferably,the average pigment particle size is no larger than 150 nm. The averageparticle size of pigment particles is preferably determined with aBrookhaven Instruments Particle Sizer BI90plus based upon the principleof dynamic light scattering.

Generally dyes exhibit a higher light fading than pigments, but cause noproblems on jettability. It was found that anthraquinone dyes exhibitonly minor light fading under the normal UV curing conditions used in UVcurable inkjet printing.

In a preferred embodiment, the colorant in the UV curable inkjet ink isan anthraquinone dye, such as Macrolex™ Blue 3R (CASRN 325781-98-4) fromLANXESS.

Other preferred dyes include crystal violet and a copper phthalocyaninedye.

In a preferred embodiment, the colorant is present in an amount of 0.5to 6.0 wt %, more preferably 1.0 to 2.5 wt %, based on the total weightof the UV curable inkjet ink.

Polymeric Dispersants

If the colorant in the UV curable inkjet ink is a pigment, then the UVcurable inkjet ink preferably contains a dispersant, more preferably apolymeric dispersant, for dispersing the pigment.

Suitable polymeric dispersants are copolymers of two monomers but theymay contain three, four, five or even more monomers. The properties ofpolymeric dispersants depend on both the nature of the monomers andtheir distribution in the polymer. Copolymeric dispersants preferablyhave the following polymer compositions:

-   -   statistically polymerized monomers (e.g. monomers A and B        polymerized into ABBAABAB);    -   alternating polymerized monomers (e.g. monomers A and B        polymerized into ABABABAB);    -   gradient (tapered) polymerized monomers (e.g. monomers A and B        polymerized into AAABAABBABBB);    -   block copolymers (e.g. monomers A and B polymerized into        AAAAABBBBBB) wherein the block length of each of the blocks (2,        3, 4, 5 or even more) is important for the dispersion capability        of the polymeric dispersant;    -   graft copolymers (graft copolymers consist of a polymeric        backbone with polymeric side chains attached to the backbone);        and    -   mixed forms of these polymers, e.g. blocky gradient copolymers.

Suitable polymeric dispersants are listed in the section on“Dispersants”, more specifically [0064] to [0070] and [0074] to [0077],in EP 1911814 A (AGFA).

Commercial examples of polymeric dispersants are the following:

-   -   DISPERBYK™ dispersants available from BYK CHEMIE GMBH;    -   SOLSPERSE™ dispersants available from NOVEON;    -   TEGO™ DISPERS™ dispersants from EVONIK;    -   EDAPLAN™ dispersants from MÜNZING CHEMIE;    -   ETHACRYL™ dispersants from LYONDELL;    -   GANEX™ dispersants from ISP;    -   DISPEX™ and EFKA™ dispersants from CIBA SPECIALTY CHEMICALS INC;    -   DISPONER™ dispersants from DEUCHEM; and    -   JONCRYL™ dispersants from JOHNSON POLYMER.

Photoinitiators and Photoinitiating Systems

The UV curable inkjet ink contains at least one photoinitiator, but maycontain a photoinitiating system including a plurality ofphotoinitiators and/or co-initiators.

The photoinitiator in the UV curable inkjet ink is preferably a freeradical initiator, more specifically a Norrish type I initiator or aNorrish type II initiator. A free radical photoinitiator is a chemicalcompound that initiates polymerization of monomers and oligomers whenexposed to actinic radiation by the formation of a free radical. ANorrish Type I initiator is an initiator which cleaves after excitation,yielding the initiating radical immediately. A Norrish type II-initiatoris a photoinitiator which is activated by actinic radiation and formsfree radicals by hydrogen abstraction from a second compound thatbecomes the actual initiating free radical. This second compound iscalled a polymerization synergist or co-initiator. Both type I and typeII photoinitiators can be used in the present invention, alone or incombination.

Suitable photoinitiators are disclosed in CRIVELLO, J. V., et al.Photoinitiators for Free Radical Cationic and AnionicPhotopolymerization. 2nd edition. Edited by BRADLEY, G. London, UK: JohnWiley and Sons Ltd, 1998. p. 287-294.

Specific examples of photoinitiators may include, but are not limitedto, the following compounds or combinations thereof: benzophenone andsubstituted benzophenones, 1-hydroxycyclohexyl phenyl ketone,thioxanthones such as isopropylthioxanthone,2-hydroxy-2-methyl-1-phenylpropan-1-one,2-benzyl-2-dimethylamino-(4-morpholinophenyl) butan-1-one, benzyldimethylketal, bis (2,6-dimethylbenzoyl)-2,4,4-trimethylpentylphosphineoxide, 2,4,6 trimethylbenzoyldiphenylphosphine oxide,2,4,6-trimethoxybenzoyldiphenylphosphine oxide,2-methyl-1-[4-(methylthio) phenyl]-2-morpholinopropan-1-one,2,2-dimethoxy-1, 2-diphenylethan-1-one or5,7-diiodo-3-butoxy-6-fluorone.

Suitable commercial photoinitiators include Irgacure™ 184, Irgacure™500, Irgacure™ 369, Irgacure™ 1700, Irgacure™ 651, Irgacure™ 819,Irgacure™ 1000, Irgacure™ 1300, Irgacure™ 1870, Darocur™ 1173, Darocur™2959, Darocur™ 4265 and Darocur™ ITX available from CIBA SPECIALTYCHEMICALS, Lucerin™ TPO available from BASF AG, Esacure™ KT046, Esacure™KIP150, Esacure™ KT37 and Esacure™ EDB available from LAMBERTI, H-Nu™470 and H-Nu™ 470X available from SPECTRA GROUP Ltd.

For safety reasons during manufacturing of a conductive pattern, thephotoinitiator is preferably a so-called diffusion hinderedphotoinitiator. A diffusion hindered photoinitiator is a photoinitiatorwhich exhibits a much lower mobility in a cured ink layer than amonofunctional photoinitiator, such as benzophenone. Several methods canbe used to lower the mobility of the photoinitiator. One way is toincrease the molecular weight of the photoinitiators so that thediffusion speed is reduced, e.g. polymeric photoinitiators. Another wayis to increase its reactivity so that it is built into the polymerizingnetwork, e.g. multifunctional photoinitiators (having 2, 3 or morephotoinitiating groups) and polymerizable photoinitiators.

The diffusion hindered photoinitiator for the UV curable inkjet ink ispreferably selected from the group consisting of non-polymericmultifunctional photoinitiators, oligomeric or polymeric photoinitiatorsand polymerizable photoinitiators. Most preferably the diffusionhindered photoinitiator is a polymerizable initiator or a polymericphotoinitiator.

A preferred diffusion hindered photoinitiator contains one or morephotoinitiating functional groups derived from a Norrish typeI-photoinitiator selected from the group consisting of benzoinethers,benzil ketals, α,α-dialkoxyacetophenones, α-hydroxyalkylphenones,α-aminoalkylphenones, acylphosphine oxides, acylphosphine sulphides,α-haloketones, α-halosulfones and phenylglyoxalates.

A preferred diffusion hindered photoinitiator contains one or morephotoinitiating functional groups derived from a Norrish typeII-initiator selected from the group consisting of benzophenones,thioxanthones, 1,2-diketones and anthraquinones.

Suitable diffusion hindered photoinitiators are also those disclosed inEP 2065362 A (AGFA) in paragraphs [0074] and

for difunctional and multifunctional photoinitiators, in paragraphs[0077] to [0080] for polymeric photoinitiators and in paragraphs [0081]to [0083] for polymerizable photoinitiators.

A preferred amount of photoinitiator is 0.1-20 wt %, more preferably2-15 wt %, and most preferably 3-10 wt % of the total weight of the UVcurable inkjet ink.

In order to increase the photosensitivity further, the UV curable inkjetink may additionally contain co-initiators. Suitable examples ofco-initiators can be categorized in three groups: 1) tertiary aliphaticamines such as methyldiethanolamine, dimethylethanolamine,triethanolamine, triethylamine and N-methylmorpholine; (2) aromaticamines such as amylparadimethylaminobenzoate,2-n-butoxyethyl-4-(dimethylamino) benzoate,2-(dimethylamino)ethylbenzoate, ethyl-4-(dimethylamino)benzoate, and2-ethylhexyl-4-(dimethylamino)benzoate; and (3) (meth)acrylated aminessuch as dialkylamino alkyl(meth)acrylates (e.g.,diethylaminoethylacrylate) or N-morpholinoalkyl-(meth)acrylates (e.g.,N-morpholinoethyl-acrylate). The preferred co-initiators areaminobenzoates.

When one or more co-initiators are included into the UV curable inkjetink, preferably these co-initiators are diffusion hindered for safetyreasons.

A diffusion hindered co-initiator is preferably selected from the groupconsisting of non-polymeric di- or multifunctional co-initiators,oligomeric or polymeric co-initiators and polymerizable co-initiators.More preferably the diffusion hindered co-initiator is selected from thegroup consisting of polymeric co-initiators and polymerizableco-initiators. Most preferably the diffusion hindered co-initiator is apolymerizable co-initiator having at least one (meth)acrylate group,more preferably having at least one acrylate group.

The UV curable inkjet ink preferably includes a polymerizable orpolymeric tertiary amine co-initiator.

Preferred diffusion hindered co-initiators are the polymerizableco-initiators disclosed in EP 2053101 A (AGFA) in paragraphs [0088] and[0097].

The UV curable inkjet inks preferably includes the (diffusion hindered)co-initiator in an amount of 0.1 to 20 wt %, more preferably in anamount of 0.5 to 15 wt %, most preferably in an amount of 1 to 10 wt %of the total weight of the UV curable inkjet ink.

Polymerization Inhibitors

The UV curable inkjet ink may contain at least one inhibitor forimproving the thermal stability of the ink.

Suitable polymerization inhibitors include phenol type antioxidants,hindered amine light stabilizers, phosphor type antioxidants,hydroquinone monomethyl ether commonly used in (meth)acrylate monomers,and hydroquinone, t-butylcatechol, pyrogallol,2,6-di-tert.butyl-4-methylphenol (=BHT) may also be used.

Suitable commercial inhibitors are, for example, Sumilizer™ GA-80,Sumilizer™ GM and Sumilizer™ GS produced by Sumitomo Chemical Co. Ltd.;Genorad™ 16, Genorad™ 18 and Genorad™ 20 from Rahn AG; Irgastab™ UV10and Irgastab™ UV22, Tinuvin™ 460 and CGS20 from Ciba SpecialtyChemicals; Floorstab™ UV range (UV-1, UV-2, UV-5 and UV-8) fromKromachem Ltd, Additol™ S range (S100, 5110, 5120 and 5130) from CytecSurface Specialties.

The inhibitor is preferably a polymerizable inhibitor.

Since excessive addition of these polymerization inhibitors may lowerthe curing speed, it is preferred that the amount capable of preventingpolymerization is determined prior to blending. The amount of apolymerization inhibitor is preferably lower than 5 wt %, morepreferably lower than 3 wt % of the total UV curable inkjet ink.

Surfactants

The UV curable inkjet ink may contain at least one surfactant, butpreferably no surfactant is present. If no surfactant is present, the UVcurable inkjet ink does not spread well on the metal sheet allowing thegeneration of thin conductive lines.

The surfactant can be anionic, cationic, non-ionic, or zwitter-ionic andis usually added in a total quantity less than 1 wt % based on the totalweight of the UV curable inkjet ink.

Suitable surfactants include fluorinated surfactants, fatty acid salts,ester salts of a higher alcohol, alkylbenzene sulfonate salts,sulfosuccinate ester salts and phosphate ester salts of a higher alcohol(for example, sodium dodecylbenzenesulfonate and sodiumdioctylsulfosuccinate), ethylene oxide adducts of a higher alcohol,ethylene oxide adducts of an alkylphenol, ethylene oxide adducts of apolyhydric alcohol fatty acid ester, and acetylene glycol and ethyleneoxide adducts thereof (for example, polyoxyethylene nonylphenyl ether,and SURFYNOL™ 104, 104H, 440, 465 and TG available from AIR PRODUCTS &CHEMICALS INC.).

Preferred surfactants are selected from fluoric surfactants (such asfluorinated hydrocarbons) and silicone surfactants. The siliconesurfactants are preferably siloxanes and can be alkoxylated, polyethermodified, polyether modified hydroxy functional, amine modified, epoxymodified and other modifications or combinations thereof. Preferredsiloxanes are polymeric, for example polydimethylsiloxanes.

Preferred commercial silicone surfactants include BYK™ 333 and BYK™UV3510 from BYK Chemie.

In a preferred embodiment, the surfactant is a polymerizable compound.

Preferred polymerizable silicone surfactants include a (meth)acrylatedsilicone surfactant. Most preferably the (meth)acrylated siliconesurfactant is an acrylated silicone surfactant, because acrylates aremore reactive than methacrylates.

In a preferred embodiment, the (meth)acrylated silicone surfactant is apolyether modified (meth)acrylated polydimethylsiloxane or a polyestermodified (meth)acrylated polydimethylsiloxane.

Preferably the surfactant is present in the UV curable inkjet ink in anamount of 0 to 0.05 wt % based on the total weight of the UV curableinkjet ink.

Inkjet Printing Devices

The UV curable inkjet ink may be jetted by one or more print headsejecting small droplets in a controlled manner through nozzles onto asubstrate, which is moving relative to the print head(s).

A preferred print head for the inkjet printing system is a piezoelectrichead. Piezoelectric inkjet printing is based on the movement of apiezoelectric ceramic transducer when a voltage is applied thereto. Theapplication of a voltage changes the shape of the piezoelectric ceramictransducer in the print head creating a void, which is then filled withink. When the voltage is again removed, the ceramic expands to itsoriginal shape, ejecting a drop of ink from the print head. However theinkjet printing method according to the present invention is notrestricted to piezoelectric inkjet printing. Other inkjet print headscan be used and include various types, such as a continuous type.

The inkjet print head normally scans back and forth in a transversaldirection across the moving ink-receiver surface. Often the inkjet printhead does not print on the way back. Bi-directional printing ispreferred for obtaining a high areal throughput. Another preferredprinting method is by a “single pass printing process”, which can beperformed by using page wide inkjet print heads or multiple staggeredinkjet print heads which cover the entire width of the ink-receiversurface. In a single pass printing process the inkjet print headsusually remain stationary and the substrate surface is transported underthe inkjet print heads.

Curing Devices

The UV curable inkjet ink can be cured by exposing them to actinicradiation, preferably by ultraviolet radiation. In inkjet printing, thecuring means may be arranged in combination with the print head of theinkjet printer, travelling therewith so that the curable liquid isexposed to curing radiation very shortly after been jetted.

In such an arrangement it can be difficult to provide a small enoughradiation source connected to and travelling with the print head, suchas LED. Therefore, a static fixed radiation source may be employed, e.g.a source of curing UV-light, connected to the radiation source by meansof flexible radiation conductive means such as a fibre optic bundle oran internally reflective flexible tube.

Alternatively, the actinic radiation may be supplied from a fixed sourceto the radiation head by an arrangement of mirrors including a mirrorupon the radiation head.

The source of radiation may also be an elongated radiation sourceextending transversely across the substrate to be cured. It may beadjacent the transverse path of the print head so that the subsequentrows of images formed by the print head are passed, stepwise orcontinually, beneath that radiation source.

Any ultraviolet light source, as long as part of the emitted light canbe absorbed by the photo-initiator or photo-initiator system, may beemployed as a radiation source, such as, a high or low pressure mercurylamp, a cold cathode tube, a black light, an ultraviolet LED, anultraviolet laser, and a flash light. Of these, the preferred source isone exhibiting a relatively long wavelength UV-contribution having adominant wavelength of 300-400 nm. Specifically, a UV-A light source ispreferred due to the reduced light scattering therewith resulting inmore efficient interior curing.

UV radiation is generally classed as UV-A, UV-B, and UV-C as follows:

-   -   UV-A: 400 nm to 320 nm    -   UV-B: 320 nm to 290 nm    -   UV-C: 290 nm to 100 nm.

In a preferred embodiment, the UV curable inkjet ink is cured by UVLEDs. The inkjet printing device preferably contains one or more UV LEDspreferably with a wavelength larger than 360 nm, preferably one or moreUV LEDs with a wavelength larger than 380 nm, and most preferably UVLEDs with a wavelength of about 395 nm.

Furthermore, it is possible to cure the ink pattern using, consecutivelyor simultaneously, two light sources of differing wavelength orilluminance. For example, the first UV-source can be selected to be richin UV-C, in particular in the range of 260 nm-200 nm. The secondUV-source can then be rich in UV-A, e.g. a gallium-doped lamp, or adifferent lamp high in both UV-A and UV-B. The use of two UV-sources hasbeen found to have advantages e.g. a fast curing speed and a high curingdegree.

For facilitating curing, the inkjet printing device often includes oneor more oxygen depletion units. The oxygen depletion units place ablanket of nitrogen or other relatively inert gas (e.g. CO₂), withadjustable position and adjustable inert gas concentration, in order toreduce the oxygen concentration in the curing environment. Residualoxygen levels are usually maintained as low as 200 ppm, but aregenerally in the range of 200 ppm to 1200 ppm.

EXAMPLES Materials

All materials used in the following examples were readily available fromstandard sources such as ALDRICH CHEMICAL Co. (Belgium) and ACROS(Belgium) unless otherwise specified. The water used was deionizedwater.

Dye-1 is a blue anthraquinone dye available as Macrolex™ Blue 3R fromLANXESS.

ITX is Darocur™ ITX is an isomeric mixture of 2- and4-isopropylthioxanthone from BASF.

EPD is ethyl 4-dimethyaminobenzoate available as Genocure™ EPD fromRAHN.

TPO is 2,4,6-trimethylbenzoyl-diphenyl-phosphineoxide available asDarocur™ TPO is from BASF.

BAPO is phenyl bis(2,4,6-trimethylbenzoyl)-phosphine oxide availablefrom BASF.

Irgacure™ 907 is2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, aphotoinitiator available from BASF.

INHIB is a mixture forming a polymerization inhibitor having acomposition:

TABLE 4 Component wt % DPGDA 82.4 p-methoxyphenol 4.02,6-di-tert-butyl-4-methylphenol 10.0 Cupferron ™ AL 3.6

Cupferron™ AL is aluminum N-nitrosophenylhydroxylamine from WAKOCHEMICALS LTD.

Macrolex™ Blue 3R is a blue anthraquinone dye from LANXESS.

DPGDA is dipropylene glycol diacrylate available as Sartomer™ SR508 fromSARTOMER.

2-HEA is 2-hydroxy ethyl acrylate from ALDRICH.

MADAME is N,N-dimethyl 2-aminoethyl methacrylate available as Norsocryl™MADAME from ARKEMA France.

EOEOEA is ethoxyethoxy ethylacrylate available as Sartomer™ SR256 fromSARTOMER.

ACMO is acryloyl morpholine available from RAHN.

VEEA or 2-(2-vinyloxy-ethoxy)-ethyl acrylate was supplied by NipponShokubai.

IDA is isodecylacrylate available as Sartomer™ SR395 from SARTOMER.

SR606A is a neopentylglycol hydroxyl pivalate diacrylate available asSartomer™ SR606A from SARTOMER.

HDDA is 1,6-hexanediol diacrylate available as Sartomer™ SR238 fromSARTOMER.

TMPTA is trimethylolpropane trimethacrylate available as Sartomer™ SR350from SARTOMER.

NPGDA is neopentylglycol (2× propoxylated) diacrylate available asSartomer™ SR9003 from SARTOMER

PETA is penta erythritol tetraacrylate available as Sartomer 295 fromSartomer.

CEA is 2-carboxyethyl acrylate from ALDRICH.

SR9054 is 2-hydroxyethyl methacrylate phosphate available as Sartomer™SR9054 from SARTOMER.

Measurement Methods 1. Cure Speed

After printing and curing on the copper plates, the inkjetted layer wasevaluated by touch of a finger. Evaluation was made in accordance with acriterion described in Table 5.

TABLE 5 Evaluation Criterion OK Layer feels not tacky Not OK Layer feelstacky or even wet

2. Etch Resistance

The etch resistance was evaluated by rubbing a cotton bud over the layerimmediately after etching and rinsing. Evaluation was made in accordancewith a criterion described in Table 6.

TABLE 6 Evaluation Criterion OK Layer not damaged Not OK Layer damaged

3. Strippability and Flakes

A punch of an etched and dried sample was submitted into a beakercontaining 6.25% NaOH-solution at 50° C. and stirred. The time ofrelease of the inkjetted layer from the copper surface, i.e. the releasetime, was measured. Evaluation was made in accordance with a criteriondescribed in Table 7.

TABLE 7 Evaluation Criterion OK Release time of less than 5 minutesModerate Release time of 5 to 10 minutes Not OK Release time of morethan 10 minutes

Once the release of the inkjetted layer started, the formation of flakesis observed. Evaluation was made in accordance with a criteriondescribed in Table 8.

TABLE 8 Evaluation Criterion OK Flake formation within 5 minutesModerate Flake formation within 8 minutes Not OK No break-down of theinkjetted layer within 20 minutes

4. Viscosity

The viscosity of the formulations was measured at 45° C. using a“Robotic Viscometer Type VISCObot” from CAMBRIDGE

Applied Systems.

For industrial inkjet printing, the viscosity is preferably between 3.0and 20 mPa·s at 45° C. More preferably the viscosity is less than 15mPa·s at 45° C.

Example 1

This example illustrates the manufacturing of conductive patterns withUV curable inkjet inks in accordance with the invention.

Preparation of the UV Curable Inkjet Inks

The comparative UV curable inkjet ink COMP-1 to COMP-11 and theinventive UV curable ink INV-1 to INV-16 were prepared according to acomposition of Type A or B in Table 9. The weight percentages (wt %)were all based on the total weight of the UV curable inkjet ink.

TABLE 9 wt % in the inkjet ink Components Type A Type B Dye-1 1.00 1.75Polymerizable composition according 86.00  82.25  to Table 4 ITX 4.005.00 EPD 4.00 — TPO 4.00 2.00 BAPO — 3.00 Irgacure ™ 907 — 5.00 INHIB1.00 1.00

The amount and type of monomers used in the polymerizable composition ofthe inkjet inks are shown in Table 10. The weight percentages (wt %) inTable 4 were all based on the total weight of the polymerizablecomposition. The viscosity was measured and is shown in Table 11.

TABLE 10 Inkjet Ink Polymerizable Composition for Table 9 Sample TypeAcryl Amide wt % Polyfunctional acrylate wt % Acid acrylate wt % COMP-1A 2-HEA 47.7 SR606A 46.5 CEA 5.8 COMP-2 A MADAME 47.7 SR606A 46.5 CEA5.8 COMP-3 A EOEOEA 47.7 SR606A 46.5 CEA 5.8 COMP-4 A 2-HEA 47.7 DPGDA46.5 CEA 5.8 COMP-5 A MADAME 47.7 DPGDA 46.5 CEA 5.8 COMP-6 A EOEOEA47.7 DPGDA 46.5 CEA 5.8 COMP-7 A ACMO 53.5 SR606A 46.5 CEA 0.0 COMP-8 BVEEA 48.9 SR606A 45.0 CEA 6.1 COMP-9 B IDA 48.9 SR606A 45.0 CEA 6.1COMP-10 B ACMO 8.8 SR606A 85.1 CEA 6.1 COMP-11 A ACMO 30.2 SR606A 46.5SR9054 23.3 INV-1 A ACMO 47.7 SR606A 46.5 CEA 5.8 INV-2 A ACMO 53.5SR606A 40.7 CEA 5.8 INV-3 A ACMO 59.3 SR606A 34.9 CEA 5.8 INV-4 A ACMO65.1 SR606A 29.1 CEA 5.8 INV-5 A ACMO 50.6 SR606A 46.5 CEA 2.9 INV-6 AACMO 52.3 SR606A 46.5 CEA 1.2 INV-7 A ACMO 47.7 DPGDA 46.5 CEA 5.8 INV-8A ACMO 47.7 HDDA 46.5 CEA 5.8 INV-9 A ACMO 47.7 NPGDA 46.5 CEA 5.8INV-10 A ACMO 47.7 TMPTA 46.5 CEA 5.8 INV-11 A ACMO 47.7 PETA 46.5 CEA5.8 INV-12 B ACMO 33.1 SR606A 60.8 CEA 6.1 INV-13 B ACMO 21.0 SR606A72.9 CEA 6.1 INV-14 A ACMO 41.9 SR606A 46.5 CEA 11.6 INV-15 A ACMO 47.7SR606A 46.5 SR9054 5.8 INV-16 A ACMO 41.9 SR606A 46.5 SR9054 11.6

Evaluation and Results

Isola™ IS400 copper plates having a 35 μm copper foil (available fromCCI Eurolam were cleaned for 5 seconds at 25° C. with a solution calledMecbrite™ CA-95 from MEC Europe, which has pH<1 and contained H₂SO₄,H₂O₂ and Cu²⁺. During this operation a thin top layer of Cu (0.3-0.5 μm)was removed. The plates were then rinsed with a water jet for 90seconds.

A pattern of the UV curable inkjet inks COMP-1 to COMP-11 and INV-1 toINV-16 was printed unidirectional by means of an Anapurna™ M inkjetprinter equipped with Konica Minolta 512 print heads at 14 pL dropvolume in 8 passes (1440×720 dpi) and cured by means of an Fe doped Hglamp with an output of 550 mJ/cm². An evaluation for cure speed wasmade, the result is shown in Table 11.

The plates were subjected to an acidic etch bath (“Mega” acid etchantobtained from Mega Electronics, pH 2, contains FeCl3) for 115 seconds at35° C. The plates were subsequently rinsed for 90 seconds with water anddried. An evaluation of the etch resistance was then made as shown inTable 11. The copper plates having their inkjet ink layer removed duringetched could naturally not be evaluated for strippability and flakeformation (in Table 11 marked as not applicable: NA).

TABLE 11 InkJet Viscosity Cure Etch Ink (mPa · s) Speed ResistanceStrippability Flakes COMP-1 6 OK Not OK NA NA COMP-2 4 Not OK OK OK OKCOMP-3 5 OK Not OK NA NA COMP-4 5 OK Not OK NA NA COMP-5 3 Not OK OK OKOK COMP-6 4 OK Not OK NA NA COMP-7 8 OK OK Not OK OK COMP-8 7 OK OK NotOK OK COMP-9 7 OK OK Not OK OK COMP-10 15 OK OK Not OK Moderate COMP-1118 OK Not OK NA NA INV-1 9 OK OK OK OK INV-2 9 OK OK OK OK INV-3 9 OK OKOK OK INV-4 8 OK OK OK OK INV-5 9 OK OK OK OK INV-6 9 OK OK Moderate OKINV-7 7 OK OK OK OK INV-8 6 OK OK OK OK INV-9 6 OK OK OK OK INV-10 13 OKOK OK OK INV-11 20 OK OK OK OK INV-12 14 OK OK OK OK INV-13 14 OK OK OKOK INV-14 11 OK OK OK OK INV-15 10 OK OK OK OK INV-16 11 OK OK OK OK

From Table 11, it should be clear that only the UV curable inkjet inkscomplying with the requirements of claim 1 exhibited excellent results.By replacing the acrylamide ACMO by other monomers that are equallyhydrophilic but are (meth)acrylates, or by ignoring the ranges for theacryl amide, the polyfunctional acrylate and the acid monomer, the UVcurable inkjet inks failed on one or more of the requirements formanufacturing conductive patterns.

1-15. (canceled)
 16. A UV curable inkjet ink comprising: a polymerizablecomposition, at least 80 wt % of the polymerizable compositionconsisting of: 15.0 to 70.0 wt % of an acryl amide; 20.0 to 75.0 wt % ofa polyfunctional acrylate; and 1.0 to 15.0 wt % of a monofunctional(meth)acrylate including a carboxylic acid group, a phosphoric acidgroup, or a phosphonic acid group; wherein all weight percentages (wt %)are based on a total weight of the polymerizable composition.
 17. The UVcurable inkjet ink according to claim 16, wherein the acryl amide is acyclic acryl amide.
 18. The UV curable inkjet ink according to claim 17,wherein the cyclic acryl amide is acryloyl morpholine.
 19. The UVcurable inkjet ink according to claim 16, wherein at least 1.5 wt % ofthe monofunctional (meth)acrylate including the carboxylic acid group,the phosphoric acid group, or the phosphonic acid group is present inthe polymerizable composition.
 20. The UV curable inkjet ink accordingto claim 16, wherein the monofunctional (meth)acrylate containing thecarboxylic acid group, the phosphoric acid group, or the phosphonic acidgroup is selected from the group consisting of 2-carboxyethyl acrylate,2-acryloyl ethyl succinate, and 2-hydroxyethyl methacrylate phosphate.21. The UV curable inkjet ink according to claim 16, wherein thepolyfunctional acrylate is selected from the group consisting ofdipropylene glycol diacrylate, neopentylglycol diacrylate,neopentylglycol (2× propoxylated) diacrylate, penta erythritol tetraacrylate, 1,6-hexanediol diacrylate, trimethylolpropane trimethacrylate,ethoxylated tmpta, tripropylene glycol diacrylate, ditrimethyloylpropanetetraacrylate, ethoxylated pentaerythritol tetraacrylate, andpolyethyleneglycol diacrylate.
 22. The UV curable inkjet ink accordingto claim 16, wherein the UV curable inkjet ink includes 0 to 0.05 wt %of surfactant based on the total weight of the UV curable inkjet ink.23. An etched metal or alloy substrate printed with the UV curableinkjet ink according to claim
 16. 24. The etched metal or alloysubstrate according to claim 23, wherein the etched metal or alloysubstrate includes copper.
 25. The etched metal or alloy substrateaccording to claim 23, wherein the etched metal or alloy substrate isselected from the group consisting of a printed circuit board and adecorative etched metal panel.
 26. A method of inkjet printingcomprising the steps of: forming a protected area on a metal surface byprinting and curing a UV curable inkjet ink on the metal surface;removing metal from an unprotected area of the metal surface by etching;and at least partially removing the printed and cured UV curable inkjetink from the protected area of the metal surface; wherein the UV curableinkjet ink includes a polymerizable composition, at least 80 wt % of thepolymerizable composition consisting of: 15.0 to 70.0 wt % of an acrylamide; 20.0 to 75.0 wt % of a polyfunctional acrylate; and 1.0 to 15.0wt % of a monofunctional (meth)acrylate including a carboxylic acidgroup, a phosphoric acid group, or a phosphonic acid group; and allweight percentages (wt %) are based on a total weight of thepolymerizable composition.
 27. The method of inkjet printing accordingto claim 26, wherein the polymerizable composition includes one or morecompounds selected from the group selected from acryloyl morpholine,2-carboxyethyl acrylate, 2-hydroxyethyl methacrylate phosphate,dipropylene glycol diacrylate, pentaerythritol tetraacrylateneopentylglycol diacrylate, neopentylglycol (2× propoxylated)diacrylate, pentaerythritol tetraacrylate, 1,6-hexanediol diacrylate,trimethylolpropane triacrylate, ethoxylated trimethylolpropanetriacrylate, tripropyleneglycoldiacrylate, and2-(2-vinyloxy-ethoxy)-ethyl acrylate.
 28. A method for manufacturing aconductive pattern comprising: the inkjet printing method according toclaim
 27. 29. A method for manufacturing a decorative etched metal panelcomprising: the inkjet printing method according to claim 27.